1. Field of the Invention
The present invention relates in general to hard disk drives, and more particularly, to a method and apparatus of providing a portable, non-contact clock assembly which can be coupled to a hard disk drive so as to provide reference signals during servo writing.
2. Description of the Related Art
Disk drives are magnetic recording devices used for the storage of digital information. The digital information is recorded on concentric tracks on either surface of one or more magnetic recording disks. Each concentric track is divided into one or more sectors in which data is recorded.
In such magnetic recording devices, "marks" are used in establishing a reference point from which informational data may be detected. These marks include address marks which indicate the start of a sector in which digital data is recorded and synchronization pulses which facilitate synchronism between the internal clock of the disk drive and the speed at which the recording disk rotates.
Typically, before any information is recorded on the disks, sectors are established, to facilitate the orderly recording and reproduction of information. Prior to establishing these sectors, reference marks are written on the outermost track of the recording disks to provide reference points for the initial formatting of the disks. This is typically accomplished using a clock head assembly which is mounted on an assembly station.
FIG. 1 illustrates a conventional servo-track writing system 10, which positions the read/write heads in a magnetic disk drive 12 from a master drive assembly 14 located on an assembly station 16. The servo-track writing system 10 includes a master drive assembly 14 which includes a master arm 18 that is controlled by a master arm motor 20. The master arm 18 controls the movement of the hard drive arm 22 through the use of a mechanical push-pin 24.
To provide positional information for the read/write heads during servo writing, a master clock head assembly 26 located on the assembly station 16 embeds reference marks in the form of index bits on the outermost track of the disk. After writing the index bits, the master clock head assembly 26 verifies the validity of the index bits. During servo writing, the index bits are read by the master clock head assembly 26 and provided to a microprocessor-based servo controller 28. The servo controller 28 generates reference signals used in controlling the read/write heads mounted on the hard drive arm 22 via electronics 30 to perform a servo write routine.
The cover of the hard drive assembly 12 is removed prior to and during the process of servo writing so that the master arm 18 and the master clock head assembly 26 can be coupled to the hard drive arm 22 and the disk surface, respectively. This is typically accomplished in an open room environment. To ensure that dust or other contamination on the disk surface is minimized, the process of writing the reference marks and the process of servo writing must be conducted in a clean room, which is adequately equipped with filters to minimize contamination. Clean rooms are relatively expensive to build and maintain. In addition, personnel conducting the servo writing process must be fitted with appropriate clothing such as gowns, hoods and gloves to minimize the risk of contaminating the disks. Furthermore, the reference mark writing process and the servo writing process are restricted to the assembly station 16 since the master clock head assembly 26 is mounted on the assembly station 16. Such typical servo writing processes are thus particularly cumbersome and expensive.
A more recent approach for providing such clock reference signals is disclosed in pending U.S. application Ser. No. 08/632,011, entitled "Method and Apparatus of providing a Captive Clock Head Assembly", filed Apr. 15, 1996, now U.S. Pat. No. 5,760,989, which is assigned to the assignee of the present invention. The captive clock head assembly includes a clock head that is mounted to an arm and coupled to the magnetic disk through a window of the disk drive housing. The arm is pivotably mounted to a housing which has a gasket that seals the window and allows the assembly to operate in a non-clean room environment. The arm is coupled to a cam that is manually actuated by a lever to move the clock head arm assembly between a loaded position and an unloaded position. An alignment plate is also provided for aligning the clock head assembly to the hard drive assembly. During servo writing, the captive clock head assembly is inserted into a slot on the side of the hard disk drive and activated to provide reference marks on the magnetic disk of the hard drive. The coupling of this captive clock head assembly onto the hard disk drive has to be conducted under a clean hood. Thereafter, servo writing may be conducted in a non-cleanroom environment.
Accordingly, there is a need in the technology for providing an apparatus and method for writing reference marks which is not restricted to an assembly station and which eliminates the need to utilize a clean room environment during assembly of the equipment or during the servo writing process.